Changes between Version 29 and Version 30 of DevelopmentActivities/MergeOCN/Vuichard

Timestamp:

2014-02-06T15:32:08+01:00 (10 years ago)

Author:

nvuilsce

Comment:

--

DevelopmentActivities/MergeOCN/Vuichard

@@ -95 +95 @@
   - pK_H2O = -log(K_H2O) = 14
   - pk_NH4 = -log(K_NH4) = 9.25
-This leads to :
+ This leads to :
  pK_H2O - pK_NH4 = log([NH4+]/[NH3]) + pH
- or [NH4+]/[NH3] = 10^(pK_H2O - pK_NH4 - pH) = 10^(4.75-pH)
+ or [NH4+]/[NH3] = 10^(pK_H2O - pK_NH4 - pH)^ = 10^(4.75-pH)
   
-In OCN, one makes use of frac_nh3. That assumes to be the NH3/NH4 ratio. It is defined [source:branches/orchidee-N/ORCHIDEE/src_stomate/stomate_soilcarbon.f90@19#L852 here] as:
+ In OCN, one makes use of frac_nh3, that is assumed to be the NH3/NH4 ratio. It is defined [source:branches/orchidee-N/ORCHIDEE/src_stomate/stomate_soilcarbon.f90@19#L852 here] as:
 {{{
 frac_nh3(:) = 10.0**(4.25-pH(:)) / (1. + 10.0**(4.25-pH(:)))
 }}}
-I have several interrogations about the equation and value used in OCN. But I have also concerns about the formulation of Li et al. ... 
- 1/ The formulation of Li et al. doesn't match with the formulas in "DISSOCIATION CONSTANTS OF INORGANIC ACIDS AND BASES" or with the formulas of http://www.onlinebiochemistry.com/obj-512/Chap4-StudNotes.html. To my opinion, one should replace log(K_NH4+) by log(K_NH3) in the formulation of Li et al. 
- With the relationship pKa + pKb = pKwater (where a and b are acid and base) this leads to [NH4+]/[NH3] = 10^(pK_NH4 - pH) = 10^(9.25 - pH)
- 2/ Wether I'm right or not about 1/, I don't understand the value used in OCN (4.25). It should be either 4.75 or 9.25 but 4.25 looks strange
- 3/ OCN used a formulation for [NH3]/[NH4+] of the type: X/(1+X) with X=[NH3]/[NH4+]. This leads to 
+ I have several interrogations about the equation and value used in OCN. But I have also concerns about the formulation of Li et al. ... 
+  1. The formulation of Li et al. doesn't match with the formulas in "DISSOCIATION CONSTANTS OF INORGANIC ACIDS AND BASES"  ([http://sites.chem.colostate.edu/diverdi/all_courses/CRC%20reference%20data/dissociation%20constants%20of%20inorganic%20acids%20and%20bases.pdf here]) or with the formulas of http://www.onlinebiochemistry.com/obj-512/Chap4-StudNotes.html. To my opinion, one should replace log(K_NH4+) by log(K_NH3) in the formulation of Li et al. With the relationship pKa + pKb = pKwater (where a and b are acid and base) this leads to [NH4+]/[NH3] = 10^(pK_NH4 - pH)^ = 10^(9.25 - pH)
+  2. Wether I'm right or not about 1., I don't understand the value used in OCN (4.25). It should be either 4.75 or 9.25 but 4.25 looks strange
+  3. OCN used a formulation for [NH3]/[NH4+] of the type: X/(1+X) with X=[NH3]/[NH4+]. This leads to 
  X/(1+X)=([NH3]/[NH4+])/(([NH4+]/[NH4+])+([NH3]/[NH4+]))
  or X/(1+X) = [NH3] / ( [NH3] + [NH4+] )
  This means that the value stored in soil_n_min(:,:,iammonium) corresponds to the total N of both [NH4+] and [NH3]. This makes sense to my opinion, but I wonder if one should not account for this partitioning between [NH4+] and [NH3] in other processes. To check.
- 4/ The X value should relate to [NH3]/[NH4+] but to my opinion the X value used in the equation in OCN corresponds to [NH4+]/[NH3]. Is this a bug ?
+  4. The X value should relate to [NH3]/[NH4+] but to my opinion the X value used in the equation in OCN corresponds to [NH4+]/[NH3]. Is this a bug ?